Previous Inductors & Inductance Practice Test Next Magnetism & Electromagnetic Induction Practice Test

BASIC NEC 2023

Kirchhoff's Laws & Series-Parallel Circuits Practice Test

Free online Kirchhoff's Laws and series-parallel circuits practice test. 25 basic electrical questions on KVL, KCL, combined resistance networks, voltage dividers, and current dividers. Good for electrician exam prep.

TOPICS COVERED

KCL Statement KVL Statement KCL Unknown Current KVL Unknown Voltage Series Resistance Recap Parallel Resistance Formula

How this test works

Read each question carefully

Look for absolute words like always / never — they often distinguish the right answer.

Manage your time

You have 38 min for 22 questions. Skip tough ones and come back.

Progress is auto-saved

Your answers are saved locally — a page refresh won't lose your work.

Review your answers

After submitting you'll see every explanation and your NEC references.

Kirchhoff's two laws are just formal versions of rules you already know. Kirchhoff's Voltage Law (KVL): the voltage drops around any closed loop must add up to the source voltage. Kirchhoff's Current Law (KCL): the current flowing into a junction must equal the current flowing out. Together they let you solve circuits too complex for Ohm's Law alone. For combined series-parallel networks, the general strategy is: simplify each parallel section into one equivalent resistance first, then add the series resistances together.

22

Questions

38 min

Time

75%

Pass

Timer starts immediately. Progress is auto-saved.

Kirchhoff's Laws & Series-Parallel Circuits Practice Test — Question List

Question 1: Kirchhoff's Current Law (KCL) states that:

The total current entering a junction (node) equals the total current leaving it
The total voltage entering a junction equals the total voltage leaving it
Current always splits equally between all branches
Current only flows in series circuits

Question 2: Kirchhoff's Voltage Law (KVL) states that:

The sum of all voltage drops around a closed loop equals the source voltage
The sum of all currents around a closed loop equals zero
Voltage is always the same at every point in a loop
Voltage only exists in parallel circuits

Question 3: At a junction, 3 A and 5 A flow IN, while 4 A flows OUT on one branch. How much current must flow OUT on the remaining branch?

2 A
4 A
8 A
12 A

Question 4: A series circuit loop is supplied by a 24 V source. Two resistors in the loop drop 10 V and 6 V. What is the voltage drop across the third resistor in the loop?

4 V
8 V
16 V
24 V

Question 5: In a SERIES circuit, the total resistance is found by:

Adding all the individual resistances together
Taking the reciprocal of the sum of reciprocals
Multiplying all the resistances together
Dividing the largest resistance by the smallest

Question 6: For a PARALLEL circuit with only two resistors, total resistance can be found using the "product over sum" formula:

R<sub>total</sub> = (R1 × R2) / (R1 + R2)
R<sub>total</sub> = R1 + R2
R<sub>total</sub> = R1 × R2
R<sub>total</sub> = (R1 + R2) / 2

Question 7: Three resistors of 12 Ω each are connected in PARALLEL. What is the total resistance?

36 Ω
12 Ω
4 Ω
3 Ω

Question 8: A 6 Ω resistor is in series with a parallel combination of a 4 Ω and a 12 Ω resistor. What is the total circuit resistance?

22 Ω
9 Ω
16 Ω
3 Ω

Question 9: A 100 V source is connected across two series resistors: 30 Ω and 70 Ω. What is the voltage drop across the 30 Ω resistor?

30 V
70 V
50 V
100 V

Question 10: A total current of 10 A splits between two parallel branches: 20 Ω and 5 Ω. How much current flows through the 5 Ω branch?

2 A
5 A
8 A
10 A

Question 11: The equivalent resistance of two or more resistors connected in PARALLEL is always:

Less than the value of the smallest individual resistor
Greater than the value of the largest individual resistor
Exactly equal to the average of all the resistors
Always exactly zero

Question 12: A circuit has a 6 Ω resistor in series with a parallel combination that works out to 3 Ω (total resistance = 9 Ω). If the source is 18 V, what is the total circuit current?

0.5 A
2 A
6 A
9 A

Question 13: For the circuit in the previous question (18 V source, total resistance 9 Ω, total current 2 A), how much power is dissipated by the ENTIRE circuit?

9 W
18 W
36 W
72 W

Question 14: Two components are described as being connected in PARALLEL when they:

Share the same two connection points, so the same voltage appears across both
Are always drawn side by side on paper
Always carry exactly the same current
Cannot be part of the same larger circuit

Question 15: Adding another resistor in PARALLEL to an existing circuit will always make the total resistance:

Decrease
Increase
Stay exactly the same
Become infinite

Question 16: Adding another resistor in SERIES to an existing circuit will always make the total resistance:

Increase
Decrease
Stay exactly the same
Drop to zero

Question 17: Kirchhoff's Voltage Law is really a more formal way of stating a rule you already know: in a single-loop series circuit, the voltage drops:

Must add up to equal the source voltage
Must always be equal to each other
Have no relationship to the source voltage
Must always add up to zero regardless of the source

Question 18: Kirchhoff's Current Law is really a more formal way of stating a rule you already know: at a parallel circuit branch point, the individual branch currents:

Must add up to equal the total current supplied
Must always be equal to each other
Have no relationship to the total current
Must always add up to zero regardless of the source

Question 19: At a junction, current enters from two branches: 7 A and 3 A. Current also enters from a third branch of unknown value, and a single branch carries 15 A out. What is the current on the unknown branch?

5 A
10 A
15 A
25 A

Question 20: In a series loop with a 48 V source, three resistors drop 12 V, 20 V, and an unknown amount. What is the voltage drop across the third resistor?

8 V
16 V
20 V
32 V

Question 21: A circuit has a 10 Ω resistor in parallel with a 40 Ω resistor, and this combination is in series with a 2 Ω resistor. What is the total circuit resistance?

8 Ω
10 Ω
12 Ω
52 Ω

Question 22: A short circuit (zero resistance) accidentally forms across one branch of a parallel combination. The most likely effect is:

Nearly all current will flow through the short, and the combination's resistance drops to nearly zero
The rest of the circuit will be completely unaffected
The total resistance of the combination will increase
Current will stop flowing entirely

EXAM CARD BASIC

Questions22

Time limit38 min

Pass score75%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 (NFPA 70)